JP7194281B2 - Electrolyte composition and secondary battery using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrolyte composition and a secondary battery using the same, and more particularly, an electrolyte composition having excellent SEI film-forming ability and HF removal ability, and improved life characteristics and high-temperature stability. , and a secondary battery using the same.

2. Description of the Related Art In recent years, with the increasing popularity of electric vehicles and portable electronic devices, the demand for lithium secondary batteries exhibiting high energy density and operating potential and low self-discharge rate is rapidly increasing.

Lithium ions released from the positive electrode active material such as lithium metal oxide during the initial charge of the lithium secondary battery migrate to the negative electrode active material and are inserted between the layers of the negative electrode active material. At this time, since lithium ions are highly reactive, the electrolyte solution composition and the material constituting the negative electrode active material react on the surface of the negative electrode active material, and SEI (Solid), which is a kind of protective film, is formed on the surface of the negative electrode active material. Electrolyte Interface) to form a coating.

The SEI coating prevents the breakdown of the structure of the negative electrode due to the insertion of organic solvent molecules having a large molecular weight, which move together with the lithium ions in the electrolyte composition, between the layers of the negative electrode active material. As a result, contact between the electrolyte composition and the negative electrode active material is prevented, so that decomposition of the electrolyte composition does not occur, and the amount of lithium ions in the electrolyte composition is reversibly maintained and stabilized. Charging and discharging are maintained.

Therefore, there is increasing interest in additives for forming a stable SEI film on the surface of the negative electrode to improve the life characteristics. In particular, cyclic fluorocarbonate-based compounds such as fluoroethylene carbonate (FEC) are excellent in the ability to form an SEI film on the surface of the negative electrode, and are widely used as a negative electrode film-forming agent for lithium ion batteries and as a co-solvent. [See Korean Patent No. 10-0977973].

However, FEC can decompose in the electrolyte to produce hydrofluoric acid (HF). Such HF may be decomposed during charging and discharging processes to release hydrogen gas. In particular, at high temperatures, such a phenomenon may deepen and cause a swelling phenomenon, and in severe cases, may even cause an explosion. In addition, HF is acidic and may cause electrode corrosion and the like.

Therefore, it is desired to develop an electrolytic solution composition that has the ability to form an SEI film, is excellent in HF removal ability, and has improved life characteristics and high-temperature stability.

An object of the present invention is to provide an electrolyte composition having excellent SEI film-forming ability and HF removing ability, and improved life characteristics and high-temperature stability.

Another object of the present invention is to provide a secondary battery using the electrolyte composition.

Meanwhile, the present invention provides an electrolyte composition comprising a compound represented by Chemical Formula 1 below, a cyclic fluorocarbonate-based compound, and a non-aqueous solvent.

In the above formula,
R is a hydrogen atom or Si[(CH ₂ ) _x CH ₃ ] _y [(CH ₂ ) _z CF ₃ ] _3-y ;
x, y and z are each independently an integer of 0-3.

In one embodiment of the present invention, R is Si[(CH ₂ ) _x CH ₃ ] _y [(CH ₂ ) _z CF ₃ ] _3-y , and x, y and z are each independently 0 It can be an integer from ~3.

In one embodiment of the present invention, the compound represented by Formula 1 may be included in an amount of 0.05 to 5% by weight based on 100% by weight of the electrolyte composition.

In one embodiment of the present invention, the cyclic fluorocarbonate-based compound may include fluoroethylene carbonate.

In one embodiment of the present invention, the cyclic fluorocarbonate-based compound may be included in an amount of 0.5-30% by weight based on 100% by weight of the electrolyte composition.

In one embodiment of the present invention, the mixing ratio of the compound represented by Chemical Formula 1 and the cyclic fluorocarbonate-based compound may be 1:1 to 1:20.

In one embodiment of the present invention, the electrolyte composition may further include a lithium salt.

On the other hand, the present invention provides a secondary battery comprising the electrolyte composition.

In one embodiment of the invention, the secondary battery may be a lithium secondary battery.

The electrolytic solution composition according to the present invention contains both a cyclic fluorocarbonate-based compound and a propanesultone compound substituted with a specific substituent, so that it has excellent SEI film-forming ability, and when applied to a battery, It has excellent room temperature life characteristics and can improve the output. In addition, the electrolyte composition according to the present invention has excellent HF removal ability, excellent life characteristics even at high temperatures, and improved high-temperature stability to improve durability.

The present invention will be described in more detail below.

One embodiment of the present invention relates to an electrolyte composition comprising a compound represented by Chemical Formula 1 below, a cyclic fluorocarbonate-based compound, and a non-aqueous solvent.

In the above formula,
R is a hydrogen atom or Si[(CH ₂ ) _x CH ₃ ] _y [(CH ₂ ) _z CF ₃ ] _3-y ;
x, y and z are each independently an integer of 0-3.

In one embodiment of the present invention, R is Si[(CH ₂ ) _x CH ₃ ] _y [(CH ₂ ) _z CF ₃ ] _3-y , and x, y and z are each independently 0 It can be an integer from ~3.

In one embodiment of the present invention, the compound represented by Formula 1 may be a compound represented by any one of Formulas 2 to 9 below.

In one embodiment of the present invention, the compound represented by Formula 1 removes HF present in the electrolyte composition due to its excellent reactivity with HF, resulting in stability, especially high temperature stability. can play a role in improving In particular, in Formula 1 wherein R is Si[(CH ₂ ) _x CH ₃ ] _y [(CH ₂ ) _z CF ₃ ] _3-y and x, y and z are each independently integers from 0 to 3 The represented compounds are preferred from the aspect of HF removal ability.

The compound represented by Chemical Formula 1 may be used after being commercially available, or may be prepared by a method known in the art.

In one embodiment of the present invention, the compound represented by Formula 1 is used in an amount of 0.05 to 5 wt%, preferably 0.05 to 3 wt%, based on 100 wt% of the electrolyte composition. may be included in If the compound represented by Chemical Formula 1 is contained in an amount less than 0.05% by weight, the SEI film-forming ability is reduced, and an effect of increasing high-temperature stability cannot be expected. When included in amounts, it can increase resistance and shorten battery life.

In one embodiment of the present invention, the cyclic fluorocarbonate-based compound forms a stable SEI coating on the surface of the negative electrode active material and acts as a co-solvent.

Examples of the cyclic fluorocarbonate compounds include fluoroethylene carbonate (FEC), 4,5-difluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,4,5-trifluoroethylene carbonate, 4,4,5 ,5-tetrafluoroethylene carbonate, 4-fluoro-5-methylethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4,5-difluoro-4-methylethylene carbonate, 4,4,5-trifluoro-5 -Methylethylene carbonate or a combination thereof, and fluoroethylene carbonate (FEC) is particularly preferred from the viewpoint of SEI film-forming ability.

In one embodiment of the present invention, the cyclic fluorocarbonate-based compound is included in an amount of 0.5 to 30% by weight, preferably 0.5 to 20% by weight, based on 100% by weight of the entire electrolyte composition. can be If the cyclic fluorocarbonate-based compound is contained in an amount of less than 0.5% by weight, the SEI film-forming ability may decrease. HF may be generated in excess.

In one embodiment of the present invention, the weight ratio of the compound represented by Formula 1 to the cyclic fluorocarbonate compound is 1:1 to 1:20, preferably 1:1 to 1:10, more preferably , 1:1 to 1:5. When the weight ratio of the compound represented by Chemical Formula 1 and the cyclic fluorocarbonate-based compound is within the above range, it is particularly advantageous for improving room temperature life characteristics, high temperature life characteristics, and high temperature stability.

In one embodiment of the present invention, the non-aqueous solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

The non-aqueous solvent is not particularly limited, and one commonly used in the art may be used. For example, as the non-aqueous solvent, a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, or other aprotic solvents may be used. These may be used alone or in combination of two or more.

As the carbonate-based solvent, a chain carbonate-based solvent, a cyclic carbonate-based solvent, or a combination thereof may be used.

Examples of the chain carbonate-based solvent include diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), and ethyl propyl carbonate. carbonate (EPC), ethylmethyl carbonate (EMC), or a combination thereof, and the cyclic carbonate solvent includes, for example, ethylene carbonate (EC), propylene carbonate, PC), butylene carbonate (BC), vinylethylene carbonate (VEC), or combinations thereof.

Examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, pentyl acetate, methyl propionate, ethyl propionate, butyl propionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone ( mevalonolactone, caprolactone, methyl formate, ethyl formate, propyl formate and the like may be used.

As the ether solvent, dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. may be used.

Cyclohexanone or the like may be used as the ketone-based solvent.

Ethyl alcohol, isopropyl alcohol, etc. may be used as the alcohol-based solvent.

Other aprotic solvents include dimethylsulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidinone, formamide, dimethylformamide, Acetonitrile, nitromethane, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and the like may be used.

The electrolyte composition according to one embodiment of the present invention may further include a lithium salt.

The lithium salt serves as a source of lithium ions in the battery and facilitates the movement of lithium ions between the positive electrode and the negative electrode.

Examples of the lithium salts include _LiPF6 , _LiBF4 , _LiSbF6 , _LiAsF6 , LiN _{( SO2C2F5} ) _{2 ,} Li _{( CF3SO2} )2N _{, LiN ( SO3C2F5} ). ₂ , _{LiC4F9SO3 ,} LiClO4, _LiAlO2 , _LiAlCl4 , LiCl, LiBr, LiI, LiB _{( C2O4} ) _{2 (} lithium _bis (oxalato)borate, LiBOB) , Li(CH ₃ CO ₂ ), Li(CF ₃ SO ₃ ), Li(FSO ₂ ) ₂ N, Li(CF ₃ SO ₂ ) ₃ C and the like. These may be used alone or in combination of two or more.

The concentration of the lithium salt may be 0.1-2.0M. When the lithium salt concentration is within the above range, the electrolyte composition may have suitable conductivity and viscosity.

One embodiment of the present invention relates to a secondary battery containing the electrolyte composition described above.

Since the secondary battery according to the present invention contains the electrolytic solution composition of the present invention containing both the cyclic fluorocarbonate-based compound and the compound represented by Chemical Formula 1, Not only is it possible to form a stable SEI film and has excellent life characteristics, but it is also excellent in stability, especially high-temperature stability, because HF generated during battery operation can be removed.

In one embodiment of the present invention, the secondary battery may be a lithium secondary battery, such as a lithium ion secondary battery.

The lithium secondary battery includes a positive electrode, a negative electrode, and the electrolyte composition described above.

The positive electrode includes a positive current collector and a positive active material layer formed on the positive current collector.
The positive electrode current collector may be used without particular limitation as long as it has conductivity without inducing chemical changes in the battery. Specifically, the positive electrode current collector includes aluminum, copper, stainless steel, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium. Alloys and the like may be used, and in particular aluminum may be used. The positive electrode current collector may have various forms such as foil, net, porous body, etc., and may have fine irregularities formed on the surface to strengthen the binding force of the positive electrode active material.

The positive electrode current collector may have a thickness of 3 to 500 μm.

The positive active material layer includes a positive active material, a binder, and optionally a conductive material.
A compound capable of reversible intercalation and deintercalation of lithium may be used as the positive electrode active material. Specifically, as the positive electrode active material, one or more of a composite oxide or a composite phosphorous oxide of cobalt, manganese, nickel, aluminum, iron, or a combination of these metals and lithium may be used. More specifically, as the positive electrode active material, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphorous oxide, etc. are used. good.

The binder binds the particles of the positive active material together and attaches the positive active material to the positive current collector. Specifically, the binder includes polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, poly Vinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like may be used.

The conductive material is used to impart electrical conductivity to the electrode, and any material having electronic conductivity without causing a chemical change can be used without limitation. Specifically, the conductive material includes carbon-based substances such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber; metal-based substances such as copper, nickel, aluminum, and silver; polyphenylene derivatives, and the like. conductive polymers such as

The negative electrode includes a negative current collector and a negative active material layer formed on the negative current collector.

The negative electrode current collector may be used without particular limitation as long as it has conductivity without inducing chemical changes in the battery. Specifically, the negative electrode current collector includes copper, aluminum, stainless steel, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium. Alloys and the like may be used, especially copper. The negative electrode current collector may have various forms such as foil, net, porous body, etc., and may have fine irregularities formed on the surface to strengthen the binding force of the negative electrode active material.

The negative electrode current collector may have a thickness of 3 to 500 μm.

The negative active material layer includes a negative active material, a binder, and optionally a conductive material.

Examples of the negative electrode active material include materials capable of reversible intercalation and deintercalation of lithium ions, lithium metal, lithium metal alloys, materials capable of doping and dedoping lithium, transition metal oxides, and the like. may be used.

The material capable of reversible intercalation and deintercalation of lithium ions may use crystalline carbon, amorphous carbon, or a combination thereof as a carbon-based material. Examples of said crystalline carbon include amorphous, platy, flake, spherical or fibrous graphite, which may be natural or artificial graphite. Examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

The lithium metal alloy includes lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn. Alloys with metals selected from the group may be used.

Materials capable of doping and dedoping lithium include Si, Si—C composites, SiO _x (0<x<2), Si—Q alloys (where Q is an alkali metal, alkaline earth metal, group 13 Elements selected from the group consisting of elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and are not Si), Sn, SnO ₂ , Sn—R alloys (the above R is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn ) and the like, and at least one of these may be used in combination with SiO ₂ . The elements Q and R include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Those selected from the group consisting of Bi, S, Se, Te, Po, and combinations thereof may be used.

Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide and lithium titanium oxide.

The binder binds the particles of the negative active material together and attaches the negative active material to the negative current collector. Specifically, as the binder, the same binder as that used in the positive electrode active material layer may be used.

The conductive material is used to impart electrical conductivity to the electrode, and any material having electronic conductivity without causing a chemical change can be used without limitation. Specifically, as the conductive material, the same material as that used for the positive electrode active material layer may be used.

The positive electrode and the negative electrode may be manufactured by a manufacturing method commonly known in the art.

Specifically, the positive electrode and the negative electrode are prepared by mixing respective active materials, a binder, and optionally a conductive material in a solvent to prepare an active material composition, and coating the active material composition on a current collector. manufacture.

As the solvent, N-methylpyrrolidone (NMP), acetone, water, etc. may be used.

The positive and negative electrodes may be separated by a separator. The separator may be used without particular limitation as long as it is commonly used in the relevant field. In particular, those having low resistance to ion migration in the electrolytic solution composition and excellent moisture-holding ability of the electrolytic solution composition are suitable. The separator may be made of a material selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), and combinations thereof, and may be in the form of non-woven fabric or woven fabric. The separator may have a pore size of 0.01-10 μm and a thickness of 3-100 μm. Said separator may be a single film or a multilayer film.

The lithium secondary battery may be manufactured by a manufacturing method commonly known in the art.

Specifically, in the lithium secondary battery, after obtaining a laminate by interposing a separator between a positive electrode and a negative electrode, the laminate is wound or folded to be accommodated in a battery container, and It may be produced by injecting the electrolytic solution composition into and sealing with a sealing member.
The battery container may be cylindrical, square, thin film, or the like.

The secondary battery may be used in mobile phones, portable computers, electric vehicles, and the like. In addition, the secondary battery may be combined with an internal combustion engine, a fuel cell, a supercapacitor, etc. to be used in a hybrid vehicle, and an electric bicycle that requires high output, high voltage, and high temperature driving. , electric tools, etc.

Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples and Experimental Examples. It should be obvious to those skilled in the art that these examples, comparative examples, and experimental examples are merely for the purpose of explaining the present invention, and that the scope of the present invention is not limited to these.

Synthesis Example 1: Synthesis of Compound Represented by Chemical Formula 4 In acetonitrile as a reaction solvent, 1.4 g of the compound represented by Chemical Formula 3 and 1,3-bis(3,3,3-trifluoropropyl)-1,3-bis(3,3,3-trifluoropropyl)-1, 3.6 g of 1,3,3-tetramethyldisilazane was reacted at 25° C. for 1 hour and then purified by vacuum distillation to obtain 2.8 g of the compound represented by Chemical Formula 4 (yield: 98%). ) was obtained.

¹ H NMR (299.87 MHz, CDCl ₃ ): δ=0.16-0.28(t,6H), 0.82-0.87(dt,2H), 2.01-2.14(m,2H), 3.14-3.18(dd,1H), 3.50 -3.55(dd,1H), 4.20-4.24(dd,1H), 4.51-4.55(dd,1H), 4.83-4.89(qui,1H)ppm
Example 1 Preparation of Electrolyte Composition After LiPF ₆ was added to a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 3:7 so as to be 1.0 M, A compound represented by the following chemical formula 2 was added in an amount of 1% by weight, and fluoroethylene carbonate was added in an amount of 3% by weight based on 100% by weight of the entire electrolyte composition. was prepared.

Example 2 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 3 below was used instead of the compound represented by Chemical Formula 2. did.

Example 3 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 2 was added in an amount of 0.05% by weight.

Example 4 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 2 was added in an amount of 3% by weight.

Example 5 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 1, except that 0.5% by weight of fluoroethylene carbonate was added.

Example 6 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 1, except that fluoroethylene carbonate was added in an amount of 20% by weight.

Example 7 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 4 below was used instead of the compound represented by Chemical Formula 2. did.

Example 8 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 5 below was used instead of the compound represented by Chemical Formula 2. did.

Example 9 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 6 below was used instead of the compound represented by Chemical Formula 2. did.

Example 10 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 7 below was used instead of the compound represented by Chemical Formula 2. did.

Example 11 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 8 below was used instead of the compound represented by Chemical Formula 2. did.

Example 12 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 9 below was used instead of the compound represented by Chemical Formula 2. did.

Comparative Example 1 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 2 was not added.

Comparative Example 2 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 1, except that fluoroethylene carbonate was not added.

Comparative Example 3 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 2, except that fluoroethylene carbonate was not added.

Comparative Example 4 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 7, except that fluoroethylene carbonate was not added.

Comparative Example 5 Preparation of Electrolyte Composition An electrolyte composition was prepared in the same manner as in Example 1, except that the compound represented by the following chemical formula a was used instead of the compound represented by the chemical formula 2. did.

Experimental example 1:
Secondary batteries were manufactured using the electrolyte compositions prepared in the above Examples and Comparative Examples, and normal temperature life characteristics, high temperature stability, and high temperature life characteristics were evaluated by the following methods. The discoloration characteristics of the electrolytic solution composition after storage were observed, and the results are shown in Table 1 below.

<Production of secondary battery>
As a positive electrode active material, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ powder, a carbon conductive material (Super-P; Timcal Ltd.) and a PVDF (polyvinylidene fluoride) binder were mixed at a weight ratio of 90:5:5. A positive electrode slurry was prepared by adding N-methylpyrrolidone (NMP) as a solvent to the resulting mixture so that the solid content was 60% by weight. The cathode slurry was coated on a 15 μm thick aluminum foil to a thickness of about 40 μm. This was dried at room temperature, further dried at 120° C., and then rolled to manufacture a positive electrode.

As a negative electrode active material, N-methylpyrrolidone was added to a mixture of artificial graphite, styrene-butadiene rubber, and carboxymethyl cellulose at a weight ratio of 90:5:5 so that the solid content was 60% by weight. A slurry was prepared. A copper foil having a thickness of 10 μm was coated with the negative electrode slurry to a thickness of about 40 μm. This was dried at room temperature, further dried at 120° C., and rolled to manufacture a negative electrode.

A secondary battery was manufactured using the positive electrode, negative electrode, and electrolyte composition and a polyethylene separator.

The prepared secondary battery was charged at a constant current of 0.2 C at 25° C. until the voltage reached 4.2 V, and then discharged at a constant current of 0.2 C until the voltage reached 2.5 V. did. Then, constant-current charging was performed at a current of 0.5C until the voltage reached 4.2V, and constant-voltage charging was performed until the current reached 0.05C while maintaining 4.2V. Then, the battery was discharged at a constant current of 0.5 C until the voltage reached 2.5 V (formation step).

(1) Normal-temperature life characteristics The secondary battery that has undergone the chemical conversion step is charged at a constant current of 1.0C at 25°C until the voltage reaches 4.2V. Constant voltage charging was performed until the temperature reached 05C. Then, the cycle of discharging at a constant current of 1.0 C was repeated 300 times until the voltage reached 2.5 V during discharging.

The capacity retention ratio (%) of each secondary battery at the 300th cycle was calculated using Equation 1 below.
[Mathematical formula 1]
Capacity retention rate [%] = [discharge capacity at 300th cycle/discharge capacity at 1st cycle] x 100
(2) High temperature voltage storage stability The secondary battery that has undergone the formation step is charged at a constant current of 1.0 C at 25 ° C. until the voltage reaches 4.2 V, and the current is maintained at 4.2 V. Constant voltage charging was performed until the battery reached 0.05C. Next, while the charged secondary battery was stored at 60° C., the voltage was measured using a multi-meter every 24 hours to measure the residual voltage of the charged state cell at high temperature, and high temperature voltage storage stability. was measured.

A voltage retention rate (%) of each secondary battery at the time of measurement on the 15th day was calculated by Equation 2 below.
[Mathematical formula 2]
Voltage maintenance rate [%] = [15th day open circuit voltage/initial open circuit voltage] x 100
(3) Discoloration property Color change after storing the electrolytic solution compositions prepared in Examples and Comparative Examples at 60°C for 15 days was observed and evaluated according to the following evaluation criteria.

<Evaluation Criteria>
○: no color change ×: color change Constant voltage charging was carried out until the current reached 0.05C while maintaining .2V. Then, the cycle of discharging at a constant current of 1.0 C was repeated 300 times until the voltage reached 2.5 V during discharging.

The capacity retention ratio (%) of each secondary battery at the 300th cycle was calculated using Equation 1 above.

As shown in Table 1, secondary batteries manufactured using the electrolyte compositions of Examples 1 to 12 containing the propanesultone compound represented by Chemical Formula 1 and the cyclic fluorocarbonate compound according to the present invention , Compared to the secondary batteries manufactured using the electrolyte compositions of Comparative Examples 1 to 5, it not only has better life characteristics at room temperature, but also exhibits excellent stability and life characteristics at high temperatures. I was able to confirm.

This is because the cyclic fluorocarbonate-based compound in the electrolytic solution composition according to the present invention forms an SEI film, and the propanesultone compound represented by Chemical Formula 1 removes HF that can be generated by the cyclic fluorocarbonate-based compound while generating electricity. It is believed that this is because the ring is opened by a chemical reaction and contributes to the formation of the SEI film.

The electrolyte composition of Comparative Example 5 exhibited a color change after being stored for a certain period of time.

Although specific portions of the present invention have been described in detail above, those of ordinary skill in the art to which the present invention pertains will appreciate that such specific descriptions are merely preferred embodiments. It is clear that they are not intended to limit the scope of the invention. A person having ordinary knowledge in the technical field to which the present invention belongs will be able to make various applications and modifications within the scope of the present invention based on the above contents.

Accordingly, the substantial scope of the invention will be defined by the claims appended hereto and their equivalents.

Claims (9)

An electrolytic solution composition comprising a compound represented by the following chemical formula 1, a cyclic fluorocarbonate-based compound, and a non-aqueous solvent ,
The electrolyte composition, wherein the cyclic fluorocarbonate-based compound is contained in an amount of 0.5 to 30% by weight with respect to 100% by weight of the entire electrolyte composition .

In the above formula,
R is a hydrogen atom or Si[(CH ₂ ) _x CH ₃ ] _y [(CH ₂ ) _z CF ₃ ] _3-y ;
x, y and z are each independently an integer of 0-3. R is Si[(CH ₂ ) _x CH ₃ ] _y [(CH ₂ ) _z CF ₃ ] _3-y , and x, y and z are each independently an integer from 0 to 3; Item 1. The electrolyte composition according to Item 1. The electrolyte composition according to claim 1, wherein the compound represented by Chemical Formula 1 is a compound represented by any one of Chemical Formulas 2 to 9 below.

The electrolyte composition according to claim 1, wherein the compound represented by Formula 1 is included in an amount of 0.05 to 5 wt% with respect to 100 wt% of the electrolyte composition. The electrolytic solution composition according to claim 1, wherein the cyclic fluorocarbonate-based compound includes fluoroethylene carbonate. 2. The electrolyte composition according to claim 1, wherein the weight ratio of the compound represented by Chemical Formula 1 and the cyclic fluorocarbonate compound is 1:1 to 1:20. 2. The electrolyte composition of claim 1, further comprising a lithium salt. A secondary battery comprising the electrolyte composition according to any one of claims 1 to 7 . 9. The secondary battery according to claim 8 , wherein said secondary battery is a lithium secondary battery.